1. Field
The present disclosure relates to a differential amplifier circuit configured to release an output voltage independently of the voltage range of a differential input voltage.
2. Description of Related Art
An example of differential amplifier circuits having a Norton amplifier is disclosed in SHIRATO Yoshio, “All About Analog ICs in Illustration” the first edition, p. 45, FIG. 2-18 (issued on Nov. 10, 1987 by Tokyo Denki University Publishing Division). Practically, each input terminal needs to be connected to an op-amp configured as a voltage follower, in order to make the impedance at the input terminal high. FIG. 11 is a circuit diagram showing the configuration of a differential amplifier circuit 100. This differential amplifier circuit 100 includes op-amps OP1, OP2, OP3, OP4 and resistor elements R1, R2, R3, R4. The op-amp OP1 functions as the Norton amplifier noted above, whereas the op-amps OP2, OP3, OP4 are each configured as a voltage follower in order to make the input impedances at the input terminals IP, IM, SG high. The input terminals IP, IM input a differential input signal. The input terminal SG inputs a reference voltage esg. The op-amp OP1 constitutes a differential amplifier in conjunction with the resistor elements R1, R2, R3, R4. An output terminal OUT releases a differential amplifier output in response to the differential input signal, based on the reference voltage esg.